This invention relates to a passive vehicle occupant restraint belt system including both a lap belt and a shoulder belt, in which the belts are automatically, easily and effectively transferred between an occupant-restraining and an occupant-releasing configuration in response to the opening and closing movements of a vehicle door, and preferably, are transferred substantially fully to the releasing configuration when the door is opened toward the opened position.
In recent years there have been many proposals for passive occupant-restraining systems for vehicles. The most common types of restraint systems are those based on restraint belts, and most of the proposed belt systems include a belt transfer mechanism which is driven by an electric motor, a mechanical lever, or a gear transmission. Many of the proposed systems, particularly those which use a mechanical drive to transfer the belt, require that the vehicle door be fully open to attain full release of the belt.
The problem of moving the belts from their restraining to their releasing positions, in cases where both a shoulder seat belt and lap seat belt are used, is complicated by the fact that the directions and distances of movement of the respective belts will not always be the same. It has therefore been necessary in the past to provide at least two driving mechanisms for moving each belt from the passenger-restraining to the passenger-releasing position. Since the space inside the door is narrow and limited, installation of these driving mechanisms tends to become bulky and complicated.
In addition, especially where a mechanical force, imparted through the opening movement of the door, is used to operate the belt moving system, there may be a further problem. Since the distance of movement of the shoulder belt is often longer than that of the lap belt, upon initial opening of the door, only the shoulder belt is moved toward its passenger-releasing position. At some point, however, movement of the lap belt must also be initiated, which results in a sharp step-up force to continue opening the door, and a jerking of the belt-moving mechanism and door.